A 52-year-old man with newly diagnosed acute myeloid leukemia (AML) is admitted for induction chemotherapy. He receives cytarabine (Ara-C) 200 mg/m² IV daily for 7 days as part of the standard 7+3 regimen. On day 3 of therapy, he develops severe mucositis, diarrhea, and a neutrophil count of 800/μL. His creatinine is 1.8 mg/dL (baseline 0.9 mg/dL). What is the most appropriate immediate next step in management?

Explanation

## Clinical Assessment of Cytarabine Toxicity ### Recognition of Cytarabine Syndrome **Key Point:** The constellation of mucositis, diarrhea, acute renal dysfunction, and severe myelosuppression on day 3 of cytarabine therapy suggests **cytarabine syndrome** (also called ara-C syndrome), a dose-limiting toxicity that can progress to life-threatening complications including pulmonary edema, hepatic dysfunction, and neurological toxicity. ### Pathophysiology Cytarabine is an antimetabolite that is phosphorylated intracellularly to ara-CTP, which inhibits DNA synthesis. High-dose regimens (>1 g/m²) and prolonged infusions increase the risk of systemic toxicity. The syndrome typically manifests 3–7 days after initiation. ### Management Algorithm ```mermaid flowchart TD A[Cytarabine therapy initiated]:::outcome --> B{Mucositis, diarrhea, renal dysfunction on day 3?}:::decision B -->|Yes| C[Assess for cytarabine syndrome]:::action C --> D[Check renal function, liver enzymes, pulmonary status]:::action D --> E{Creatinine elevated, myelosuppression severe?}:::decision E -->|Yes| F[Hold further cytarabine doses]:::action E -->|Yes| G[Consider dose reduction or discontinuation]:::action F --> H[Supportive care: hydration, antiemetics, G-CSF]:::action H --> I[Restart at reduced dose if toxicity resolves]:::action B -->|No| J[Continue standard dosing]:::action ``` ### Why Immediate Action Is Critical **High-Yield:** Cytarabine syndrome can rapidly progress to **pulmonary edema, acute respiratory distress syndrome (ARDS), and death** if not recognized and managed promptly. Early cessation of the drug and aggressive supportive care (hydration, corticosteroids for severe cases) are life-saving. ### Renal Dysfunction as a Red Flag The rise in creatinine from 0.9 to 1.8 mg/dL indicates acute kidney injury, which: - Impairs cytarabine clearance, leading to accumulation and worsening toxicity - Is a cardinal feature of cytarabine syndrome - Mandates dose adjustment or discontinuation **Clinical Pearl:** In this patient, continuing the standard dose would be dangerous; the drug accumulation in the setting of renal impairment will amplify toxicity. ### Supportive Measures Once cytarabine is held: - IV hydration to promote renal clearance - Antiemetics (5-HT3 antagonists, NK1 antagonists) - G-CSF to accelerate neutrophil recovery - Prophylactic corticosteroids (dexamethasone 8 mg daily × 3–5 days) may reduce syndrome severity [cite:Harrison 21e Ch 89]